Hardinge



H. HARDINGE Aug. 14, 1956 PROCESS AND APPARATUS FOR CLASSIFYING MATERIAL Filed Feb. 27, 1953 3 Sheets-Sheet l Aug. 14, 1956 H. HARDINGE 2,758,713

PROCESS AND APPARATUS FOR CLASSIFYING MATERIAL Filed Feb. 27, 1955 s Sheets-Sheet 2 Aug. 14, 1956 H. HARDINGE 2,758,713

PROCESS AND APPARATUS FOR CLASSIFYING MATERIAL Filed Feb. 27, 1953 3 Sheets-Sheet 3 INVENTOR.

United States Patent PRG'CE'SS AND APPARATUS FOR MATERIAL- Harlowe, Hardinge,. York, Pa.

Application February 27, 1953; Serial No. 339,271

Claims. (Cl. 209-144).

v This invention relates to a process and apparatus for classifying pulverized. material.- and' particularly for separating relatively coarse particles. of material of a predetermined range. of sizes from a. fluid stream: containing; a mixture of said particles. with relatively finer. sizes of material't Said process and: apparatus are particularly useful with grinding mills but it is to be understood that the same are. not to be restricted: to use with suchma.- chines and. in fact, have other. applications. of. use.

- Many types of material classifiers are in use at present and alarge number of the same are of. the type in which no moving parts, or substantially no moving parts, are used in the classifier, whereby the force of the incoming stream of fluid must be relied upon toinduce all. separation action which takes place within the classifier. Classifiers of this type are shown. and described, for example, in prior Patents Nos. 1,709,848,, 1,721,594 and 23811354. While these types of classifiers have proven commercially successful, the present invention olfers. marked advantage thereover as to; efiiciency of operation, reduction in wear of theapparatus, and decreased power requirements.

One.- problem usually encountered in. classifiers is that of stratification and agglomeration of the. material. during thepassage thereof through the apparatus. Various attemptshave been made to reduce: this tendencybut thus far the efficiency of. said attempts. has not been of the desired: degree and many of, the classifiers have been;- of expensive and complicated construction.

It. is. the principal object of the present. invention. to providea process and apparatus for classifiying pulverized material and particularly for separating; relatively coarse material: from relatively fine material entrained as a mixture in. a fluid stream, said process and: apparatus resulting in: substantially no stratificat-ion, and agglomeration of the particles as they pass through the. apparatus.

Ancillary to the. foregoing object, the process and apparatus: of the present invention contemplate the use of a. power driven: agitator which not only forcibly removes the coarser particles from a. fluid stream ofv material' but said stream. is also subjected tov a. winnowing action to render the separation of the coarser from the; finer material more efiicient, said agitator also: producing currents within the stream which move into contact with the. agitator means.

Another object; of: the invention isto. introduce a fluidv stream containing mixed. particles into classifying apparatus preferablyunder force: from a blower, a partial vacuum: also. being utilized. in the;- preferred embodiment of the. invention further to induce movement. of the. streamthrough the apparatus; whereby" no elevator is required.

A. further object of the invention is: to provide a. process and apparatus by which the. coarser particles in a fluid stream of mixed particles are positively separated. there:- from by centrifugal: force;

As anadjunct ofthe: foregoing object, the process and apparatus contemplate in the preferred embodimenttofthe ice invention the use of deflecting means which. initially cause. separation of at. least the. coarsest: particles from. the. stream, whereby the: other separating, mechanism. of the apparatus is. not burdened with. all of the coarse particles orginally within the stream.

Still another object. of the invention is to. provide a process. and apparatus by which a fluid stream of en.- trained particles of various sizes is moved into a casing. and impeller or agitator means are movable within. said casing; so as positively to impinge the coarser particles in said stream against the casing walls, from which they move preferably by gravity to collecting-means.

One further object of the invention. is to provide a process and apparatus which maybe suitably regulated and varied so as to be. capable ofproducing products over a. wide range in fineness, which. are maintainedv quite uniform in size over a substantially wide range in variables as tomaterial loads and size of particles within the stream. 7

Still. another objectof. the invention is toprovide a classifying apparatus, while far more efiicient and. economical in operation than classifiers heretofore. used, is: relatively simple and inexpensive. to construct, and wear. upon the various parts is reduced to. a minimum.

An additional object of the invention is. to. provide. in the classifying apparatus a support. for the movable agi-- tator or impeller which is so arranged relative. to the. outlet. of the classifier casing, and said outlet is also so constructed, that the. fluid stream, which is subjected to rotating action within the classifier, is. caused to move in the same. general direction of rotation. upon entering, said outlet, whereby any pressure drop within the stream. exits ing through said outlet is maintained ata minimum. This arrangement also results: in minimizing wear and power consumption. in this part. of the apparatus. and less. head room is also required in the. outlet mechanism as. compared with other classifiers heretofore. used.

Details of the foregoing, objects and. of the invention, as well as other objects thereof, are set forth in the following specification and illustrated. in the accompanying drawings comprising a part.- thereof.

In the drawings:

Fig. l is a side elevation, partly in section, illustrating one. embodiment of classifying apparatus. incorporating the principles of the present invention.

Fig. 2 is a fragmentary, diagrammatic plan view of the. upper portion of the apparatus illustrated in Fig. 1..

Fig. 3 is. a. side. elevation, partly in section, illustrating; another embodiment of apparatus. utilizing the principle of the present invention.

Fig. 4 is. a vertical sectional view of' the embodiment. shown in Fig. 3 taken on the line 4-4 thereof.

Fig. 5 is a vertical elevation, partly in section, of still another embodiment of the apparatus utilizing the principles of the present invention.

Fig. 6. is a side elevation, partly insection, of one further. embodiment of apparatus utilizing the principle of the present invention.

Fig. 7 is; a vertical sectional view taken on the line '7.-7 of Fig, 6"

Fig; 8' is a vertical elevation, partly in section, of. an exemplary classifying. system including classifying. apparatus. embodying the. principlesv of thepresent. invention- Fig. 9 is a diagrammatic. topplan view of. the. apparatus. system illustrated in Fig. 8.

The process comprising the present invention, may be performed in a number of different specific types of apparatus, certain embodiments. of which are shown in the drawings and described hereinafter, all of said embodiments utilizing the same basic principles of the invention.

Referring to Fig. 1, wherein one embodiment: of classifying apparatus is shown, a casing 12 is provided which is generally frusto-conical in this embodiment, the axis of the casing extending substantially vertically. The lower end portion of the casing 12 is connected to a collector 14 which receives coarser particles separated from a fluid stream in which said particles were entrained as will be described in detail hereinafter.

Extending upward through the collect-or 14 is an inlet or entrance conduit 16. Said conduit extends preferably axially of the casing 12. The top of .the casing 12 is closed by cover 18 through which an exhaust conduit 20 extends substantially vertically and preferably in axial alignment with the casing 12. A shaft 22 extends into the conduit 20 and is rotatably supported by suitable bearings 24 fixed relative to the conduit 20. A motor 26, which is preferably of the variable speed type, is fixedly supported relative to the conduit 21 and a belt 28 connects suitable pulleys on the motor 26 and shaft 20 as clearly shown in Fig. 1, whereby the motor drives the shaft 20.

An agitator or impeller 30 is fixed to the lower end of shaft 22. Said impeller 30 comprises in this embodiment a pair of plate-like members 32 and 34 which extend transversely to and are also fixed to the shaft 22 in longitudinally spaced relationship to each other. A plurality of elongated vanes 36 extend between and are secured to the plate-like members 32 and 34, said vanes preferably being spaced peripherally even distances around said members and the outer edges of the vanes 36 are also preferably disposed substantially parallel to the side walls of the casing 12. In the embodiment shown in Fig. 1, this is made possible by the member 34 having a larger diameter than member 32.

The impeller will function to achieve desirable results, in accordance with the present invention, which are described in detail hereinafter when only the members 32 and 34 and vanes 36 are fixed thereto, but the efficiency of the apparatus, and correspondingly of the process, is increased by providing a shield means 38 which preferably is a cone of suitable material such as sheet metal and extends between the members 32 and 34 as well as between the vanes 36 adjacent the inner edges thereof. This arrangement produces a well defined annular space or passage 40 between the casing 12 and the impeller 30. Extending tangentially from and communicating with the outlet conduit 20 is another conduit 42 and the upper end of the conduit 20 is closed by a cover or plate 44 which may be co-extensive with the upper wall of the conduit 42 as shown in Fig. 1.

While a classifier of the type described above and illustrated in Figs. 1 and 2 is useful to perform various kinds of classifying operations, it is particularly useful in a pulverizing and classifying system. One such exemplary system is illustrated in Figs. 8 and 9 wherein the classifier 10 is illustrated in sectional view. Said system may be used in conjunction with a mill, not illustrated, if desired. In any event, it is contemplated that material to be classified is in the form of a fiuid stream in which a relatively wide range of particles of pulverized material is entrained and said stream is introduced through entrance 46 to the system. As illustrated herein, said entrance has a balanced airlock 48 operatively positioned so as to control the inlet of material to the uptake conduit 50. The system also includes a blower 52 which discharges air in a direction to flow upwardly through the conduit 50 and thereby carry the fluid stream in which the pulverized material is entrained to the classifier 10. It has been found in actual practice that, depending of course upon the force of the exhaust of the blower 52, the fluid stream discharging from conduit 54) and the classifier 10 is capable of carrying particles of relatively large size of the order of an inch or more in diameter to the classifier 10. Of course a wide range of smaller sizes of particles are also entrained in said stream moving to the classifier.

Referring particularly to Fig. 1, it will be seen that the fluid stream 54 of entrained particles enters the casing 12 in a substantially vertical path and impinges against the surface of the plate-like member 32 which is preferably planar and imperforate and transverse to the path of the stream. At least the coarsest of the particles within the stream will be deflected transversely and will be impinged against the side walls of the casing 12 as indicated, for example, by the broken line arrows 56. The rotation of member 32 enhances this function. Said separated coarser particles will hit the sides of the casing 12 and fall by gravity down said sides into the collector 14. The material collected in collector 14 is discharged through the oversize spout and airlock 58.

The stream of material from which some of the coarser particies have thus been removed then moves upward through the space 40 which is defined by the casing 12 and the impeller 30. Said impeller will of course be rotated at a speed suitable to achieve greatest efiiciency during the classifying operation. The vanes 36 of the impeller will engage other relatively coarse particles within the stream moving generally upward through the space 40 and will cause them to be thrown or impinged against the sides of the casing 12 and from there said particles will move into the collector 14 by gravity.

It will be noted that the passage 40 is relatively long and the vanes 36 also act continually to disturb and break up any tendency for unbalanced loading of one portion of the classifier as opposed to another, whereby the air velocities are more evenly distributed than is otherwise possible and the air loadings are maintained substantially constant when air is used as the fluid medium. In addition, the buoying elfect of the air and the centrifugal force caused by the rotating member is maintained substantially constant with the result that the coarser particles which are thrown out of the stream by the vanes of the impellers are kept substantially clean of the fines which would otherwise tend to be entrained with them in an unbalanced load. Thus, the coarse particles in settling and moving downward into the collector 14 contain a very minimum of fines.

The fines, together with the finer particles of oversize, travel upward between the vanes 36 and through the space as the stream rises toward the outlet conduit 20. In the particular embodiment shown in Figs. 1 and 8, wherein a conical type casing 12 is shown, the diverging eflfect of the vanes 36 causes an increase in the velocity of the stream and the centrifugal force produced by the impeller 30, thus producing further refinements and classification of the particles in this portion of the apparatus without the heavy loading of coarser particles which have been removed from the stream before the material reaches the upper zone thereof.

Vanes 36 also produce a winnowing action which causes the stream to assume a somewhat wavering but generally upward path indicated by the solid arrow lines 60, said stream containing the fines intermingled with relatively finer particles of oversize. Some of the latter are caused to be thrown from the stream by vanes 36 so as to impinge against the walls of the casing 12 as indicated by the broken line arrows 62. These particles move down the walls of the casing 12 by gravity as indicated by other broken line arrows 62. The vanes 36, in conjunction with the deflecting action of member 32, cause the stream first to move toward the side walls of the casing 12 and said stream is then waveringly deflected inward toward the impeller 30 which causes engagement of the coarser oversize particles in said stream with the vanes 36. The centrifugal force of the impeller will also cause diversion of the stream back toward the walls of the casing 12 from which said stream is subsequently deflected back toward the impeller preferably a plurality of times as indicated by the arrows and resulting in a combined winnowing and deflecting effect upon the stream passing through the space 40. Further, inasmuch as the space 40 is conical and the stream 54 of entrained particles is introduced at a substantially constant rate, the velocity of said stream in cross-sectional areas will vary as said stream moves upward through the angular path thereof. This also produces variations in the winnowing effect to which the stream is subjected as it moves upward.

As has been stated herein above, the operation of this type of classifier is relatively eflicient even when the shield means 38 is omitted. However, a more eflicient cleaning of the oversize particles results if the shield 38 is embodied in the impeller 30. Said shield also more precisely defines the annular space or passage 40 which tends to decrease the consumption of power and wear on parts in this zone by eliminating a space where turbulence is caused but which performs little or no useful purpose.

It has also been found that if the perimeters of the members 32 and 34 extend somewhat beyond the shield 38, as shown in Fig. l, the passage of the fluid stream between the edges or perimeters of said members and the casing 12 is restricted to a greater degree than the restriction between shield 38 and casing 12. Thus, the velocity of the stream past the perimeters of the platelike members 32 and 34 is increased and such increase in velocity also enhances the winnowing and hindered settling action of the particles within the stream as compared with the operation of a construction in which said members 32 and 34 do not extend beyond the shield 38.

From Fig. l particularly, it will be seen that the upper member 34 is spaced a substantial distance from the cover 18 of casing 12, as well as outlet conduit 20. In view particularly of the conical configuration of casing 12, an enlarged zone 64 is provided in the upper portion of casing 12. The upper ends of the vanes 36 extend upwardly beyond the member 34 a substantial distance into the zone 64. Further, in the preferred embodiment of the invention, the lower end of outlet conduit 20 projects into zone 64 so that the fluid stream containing entrained fines which are to be removed through conduit 20 travels upward into zone 64 as shown by the arrows 60. Said stream then moves downward toward the upper surfaces of member 34 so as to be able to enter the lower end of conduit 20. Under these circumstances, member 34 acts as a bafiie. Portions of said stream are impelled by the upper ends of the vanes 36 particularly in such a way as to produce eddy currents 66 which tend somewhat to wrap around the upper ends of the vanes, as shown by the arrows indicating these currents, and said currents tend also to curve toward the upper surface of the member 34 with the result that the coarser particles thereon are thrown against the upper surface of member 34.

This deposit of coarser particles may be discharged from the member 34 by centrifugal force induced by the rotation of the impeller 30 if the speed thereof is sulficient for such purpose. However, under some circumstances, depending on the loading of the stream and the speed at which said stream is introduced to the classifier, the rotational speed of the impeller 30 may be such that insufficient centrifugal force is developed to produce the desired amount of discharge of the coarser particles from member 34. To insure substantially complete removal of said coarser particles from member 34, scraper 68 is supported adjacent said upper surface, for example, by a bracket 70 fixed to conduit 20. Said scraper is preferably positioned at a suitable angle Within a plane parallel to member 34 so as to insure scraping and discharge of the coarser particles from the upper surface of member 34 and cause the same to fall against the walls of the casing 12 and slide down the same into the collector 14.

While it is difiicult to determine exactly what takes place in the enlarged zone 64 of the classifier, tests in transparent models tend generally to indicate that two forces seem to be exerted upon the stream in said zone. One of these is the force of the stream passing through the classifier from the entrance conduit 16 to the outlet conduit 20 and the other force is centrifugal and created by the rotation of the vanes 36. The result appears to be an inward-and downward thrust of the stream with the finer particles entrained therein that have not previously settled. In this zone, a sharp degree of classification appears to take place due to the difference in the inertia of the particles within the stream. The coarser particles tend to go to the point where there is less agitation and this is near the top of member 34 as indicated by the arrows 66. At or just above the rotating member 34, the agitation seems to be greatly reduced with the result that the coarser particles in the stream drop out and are either deposited or are thrown by centrifugal force from the member 34 as described above. These particles move through the vanes 36 and fall to the walls of the casing 12, down which they slide to the collector 14 as described hereinabove.

The fluid stream from which the coarser particles have been removed and in which fines are still entrained, flows upward through outlet conduit 20 and into take-off conduit 42. Impeller 30 causes a rotational movement of the stream and said rotation is in such a direction as naturally to enter the take-01f conduit 42 which extends tangentially from the side of conduit 20 which would naturally receive the rotating stream, as clearly shown in Figs. 2 and 9. This arrangement results in minimizing any pressure drop at the outlet or exhaust end of the classifier and also minimizes frictional losses, thus resulting in decreased wear and power consumption in this portion of the system. Further, less head room is required as compared with conventional systems of this nature and a very effective and simple mounting for the impeller and drive means therefor is also made possible.

While the outlet conduit and take-off arrangement described above has been shown embodied in a classifier having a power driven impeller, it is to be understood that said arrangement may be included with similar beneficial advantage in classifiers in which no power driven impellers are used but stationary vanes or other means cause whirling of the fluid stream within the classifier. The tangential nature of the take-off conduit which naturally receives the swirling stream as it exits from the classifier casing permits marked reduction in head room of the exhaust conduit, regardless of the specific type of means which produces the swirling of the stream.

Take-off conduit 42 is illustrated in Fig. 8 as conducting the stream of fines into a separator 72 which separates the fine product from the fluid, such as air, in a manner well known in the art. The fine product is then recovered through a suitable airlock 74. The air thus freed of the fine product is returned to the blower or fan 52 through conduit 76. Thus, the blower 52, being in communication with conduit 76, separator 72, and conduit 42, places a suction upon the outlet conduit 20 and thereby facilitates movement of the fluid stream from the classifier 10 into the outlet conduit 20. Flow of air through the system illustrated in Figs. 8 and 9 is also controllable by damper 78 in a well known manner in systems of this nature. Back pressure produced by the damper 78 is suflicient to create a negative pressure on the other side of the damper 78, thus putting the system under a partial vacuum as is well known in the art. Any leakage entering the system through the various air-locks or otherwise is vented through a suitable pipe 80, which venting is controlled by damper 82 at the only point in the system under pressure.

The foregoing description has been concerned with the embodiment of a classifier illustrated specifically in Figs. 1 and 2 and included in a complete exemplary classifying system illustrated in Figs. 8 and 9. Other types of classifiers may utilize the principles of the present invention incorporated in the embodiment of classifier illustrated in Figs. 1 and 2. One such additional embodiment is illustrated in Figs. 3 and 4 wherein a substantially horizontal and cylindrical casing 84 is shown supported by any suitable means, not illustrated. Depending from the lower 7 portion of and communicating with said casing 84 is a material collecting sump 86, the walls of which converge at the bottom to communicate with an outlet 88. Said outlet may have an airlock attached thereto if desired for purposes of controlling the discharge therefrom of coarse particles of material separated fromthe stream which enters the casing by inlet conduit 90. The impeller 92 in this embodiment includes a horizontally extending shaft 94 which is supported at its opposite ends by suitable bearings 96. The inner bearing 96 is supported by a suitable narrow bracket 97 which offers a minimum of impedance to movement of the fluid stream. Shaft 94 extends axially through the outlet conduit 98 which communicates preferably tangentially with take-ofl conduit 100.

Impeller 92 has a transversely extending member 102 which is preferably plate-like and corresponds in function to the member 32 of the embodiment shown in Figs. 1 and 2. A plurality of vanes 104 are circumferentially spaced around the impeller and project substantially radially from the axis thereof. Said vanes are also relatively long and preferably substantially parallel to the side walls of the casing 84. The outer edges of said vanes are spaced from said casing walls so as to provide a substantially annular space 106 which corresponds in function to the space 40 of the embodiment of Figs. 1 and 2. Shield means 108 preferably extend between the vanes 92 adjacent the inner edges thereof and said shield means also extends longitudinally from the member 102 toward the outlet end of the casing 84 but terminates short of the ends of the vanes 92 nearest the outlet end of the casing, as clearly shown in Fig. 3. It will be understood that the shaft 94 and the member connected thereto is driven by suitable power means not shown but which may be similar to that illustrated in Figs. 1 and 8.

In the embodiment shown in Figs. 3 and 4, some of the coarser particles will be deflected from the incoming stream upon engaging the deflecting member 102 and will be impinged against the walls of the casing 84 and fall therefrom into the collecting sump 86. The stream which is thus relieved of some of said coarser particles then travels in a wavering manner through the space 106 generally as indicated by the solid line arrows 110. Particles are engaged by the vanes 92 and the coarser sizes are impinged against the sides of the casing while the stream containing the finer sizes continues to move generally longitudinally through the space 106 toward the exhaust conduit 98. The oversize particles thus separated from the stream fall to the collecting sump 86 as generally indicated by the broken line arrows 112. The stream thus freed of oversize particles but within which fines are still entrained passes into outlet conduit 98 and associated conduit 100. From conduit 100 the stream may pass to a suitable mechanism such as separator 72 shown in Fig. 8, for example. Except for the horizontal arrangement thereof, the general function of the impeller and the classifier of the embodiment shown in Figs. 3 and 4, and particularly prevention of agglomeration and stratification, as well as efficiency of separation of the coarser from the fine particles, is similar to the function of the impeller and classifier comprising the embodiment shown in Figs. 1 and 2. Further detailed description of these functions therefore is omitted in order to save repetition.

A still further embodiment of classifying apparatus is illustrated in Fig. 5, this embodiment utilizing a cylindrical casing 114 similar to that shown in Figs. 3 and 4 except that the casing is mounted so as to extend vertically and the coarse particle collector depends from the lower end thereof. The shaft 116 of the impeller 118 also extends vertically. Inlet conduit 120 introduces to the casing 114 the stream containing entrained particles which are to be classified. These particles first encounter a transversely extending deflector 122 which deflects the coarser particles therefrom unto the walls of the casing 114, as indicated by the broken line arrows, and into a particle collector 124 as in the previously described embodiments. The impeller 118 comprises a series of circumferentially spaced vanes 126 which extend upward from the deflector 122. In this embodiment, however, no shield is illustrated between the vanes as in the previously described embodiments. However, the deflector 122 first causes the stream to be deflected outward against the walls of the casing 114 and further movement of the stream in an axial direction upward in accordance with the arrows 128 results in said stream moving toward the axis of the impeller so that said stream encounters the vanes 126 with the resulting separation of coarse particles therefrom by impingement as described in regard to the previously described embodiments.

There is also somewhat of an entwining of the upwardly moving stream about the vanes 126 similar to that described relative to the upper ends of the vanes in the embodiment illustrated in Figs. 1 and 2. Thus, in general, the centrifugal force induced by the rotation of the vanes 126 causes movement of the stream outward toward the casing 114 and from there it moves backward toward the vanes farther along the generally longitudinal pathway taken by the stream in moving from the inlet conduit 120 to the outlet conduit 130 at the upper end of the casing 114. A winnowing action is produced by the impeller and, simultaneously, coarser particles entrained within the stream are physically engaged by the vanes 126 to impinge said particles against the walls or" the casing 114 from which they fall into the particle collector 124, thereby effectively removing said particles from the stream of material ascending generally upwardly through the casing 114.

The stream of material which contains principally relatively fine particles, as it reaches the upper enlarged zone 132 of casing 114, enters the outlet conduit with a circular movement induced by the impeller 118. T ake-off conduit 134 communicates tangentially with conduit 130 in a direction naturally to receive the rotatably moving stream with the same benefits as explained above in regard to the previously described embodiments of the invention.

it will be understood of course that the classifying apparatus illustrated in Fig. 5 may be substituted for the apparatus 10 incorporated, if desired, in a classifying system such as that illustrated in Fig. 8, for example. While the impeller 118 has no shield embodied therein, the vanes are nevertheless effective to produce a highly desirable winnowing action and separation of a predetermined range of relatively coarse oversize particles from the stream of material in which they were originally entrained.

One further embodiment of classifying apparatus which includes the principles of the present invention is illustrated in Figs. 6 and 7. In this embodiment, the casing 136 is conical and the same is supported in such a manner that the axis thereof is substantially horizontal. An entrance conduit 138 communicates with the smaller end of the conical casing and a fluid stream in which particles of various sizes are entrained enters the casing through said conduit. The opposite end of the casing 136 is covered by a closure 140 and centrally of said closure an outlet conduit is disposed so as to communicate with the interior of the casing. Take-off conduit 144 tangentially communicates with outlet conduit 142 in the same manner that the outlet conduits of the other embodiments communicate with the additional conduits interconnecting thereto.

An impeller shaft 146 substantially coincides with the axis of the casing 136 and extends into said casing longitudinally through the outlet conduit 142. Suitable bearings 148 are fixedly supported relative to the casing and outlet conduit for purposes of rotatably supporting opposite ends of the shaft 146. The bearings 148 which support the inner end of said shaft may be mounted on a suitable bracket 150, for example, which is connected to the casing 136. Said bracket is of minimum width so as to afford stream into the casing 136.. The impeller 152 comprises aplurality of transversely extending. members 154 and 1'56 which are. fixed to shaft 146 in spaced relationsl'iip to each other, said members being similar to the members 32 and 34. of the embodiment shown in Fig. 1.. A plurality of vanes 158 are circumferentially spaced about the perimeters of the members 154 and 156 in parallelism and spaced relationship to the. side walls of casing 136, as in the embodiment shown in Fig. 1.

The larger end of the casing 136 is: provided with a depending sump 160 which is. provided at its lower end with. an airlock 162. Thus, as the impeller 152 is rotated,

it. causes a. winnowing of the fluid stream which moves generally longitudinally oi? the casing 136' and. said win-- nowingt induces a wavering" movement of the stream, as indicated by the solid line arrows in Fig. 6, similar to that described in the embodiment shown in: Figs. 3 and 4. Simultaneously, the blades 1'58 engage the coarser oversize particles' within the fluid stream and cause said particles toimpinge against the walls. of casing 1:36 and move by gravity to the sump 160 as indicated by the broken line arrows. in Fig. 6; Said particles exit through the airlock 162 while the stream containing principally fines of desired predetermined size passes. into. the. outlet conduit 142 and rises through the incoming conduit 144. From there the stream may pass to any suitable apparatus such as a separator 72 in a classifying system shown, for example, in Fig. 8-.

It. will be observed that no shield means is shown in the impeller 152 but such impeller nevertheless functionswithacceptable efficiency in a manner similar to the embodiment illustrated in Fig. wherein no shield means is embodied in the impeller; It will be understood however that, if desired, shield means may be incorporated in the impellers of both of these embodiments and the chiciency of the classifying function of the apparatus will correspondingly be increased for the reasons stated hereinabove. Otherwise, the separation of the coarser oversize particles from the incoming stream. by the apparatus in Figs. 6 and 7, as well as the winnowing action of the impeller, and the prevention of agglomeration and stratification, is similar to that which takes place in the other engaodiments and particularly that illustrated in Figs. 3 an .4.

It will be seen from the foregoing that all of the various embodiments described above and illustrated in the draw ings incorporate the same basic principles which include, for example, the initial deflection of the coarser particles from the incoming stream upon the same being introduced to the classifier casing so as to decrease the particle burden in the stream as it is subjected to further classification, formation of the stream substantially into an annular configuration and causing said stream to move toward the walls of the casing and from there inwardly toward the impeller as said stream progressively moves generally longitudinally of the casing toward the outlet end thereof, whereby the stream moves generally in a wavering path and winnowing is effected while the coarser oversize particles in the stream are engaged by the vanes of the impeller or are otherwise blown by centrifugal currents induced by said vanes so as to cause said particles to impinge against the walls of the casing, whereupon said particles move downward by gravity along said walls or otherwise to suitable collecting means. The speed of the impeller can be varied in order to render the air velocities within the casing evenly distributed and the air loads maintained substantially constant in order that the buoying effect of the air and the centrifugal force caused by the rotating member is maintained substantially constant. This also results in the coarser particles which are removed from the stream being kept relatively clean of fines which would otherwise tend to mingle with them in an unbalanced load. Further, the higher the speeds, the greater are the forces exerted and the finer the product delivered from the system.

While no specific means other than a variable speed motor have been described. herein: for varying the. speed: of the: impeller, it will be understod that any one of a number of other standard. expedients may be utilized such for example. as expansible V-pulleys or a variable gear born between the motor anddrive shaft of the impeller.

Byincluding a power driven impeller with the classifier, it is found that power consumption is less than in commonly used classifiers wherein air is passed through the classifier by suitable blower meansonly for example, and the force. of the air itself is required: to cause any cen-- trifugal or other action to. throw out the oversize particles; Thus, in the. herein described classifiers as well as a, system: embodying the same, there is less wear on the apparatus unit, conduits and the system generally due to the fact that the streamv containing entrained particles may be moved throughthe. system at a lower rate lOf speed than is required in. the above described classifiers which have no rotating impellers.

One of the most beneficial results of the process resulting from the various embodiments of classifiers illustrated herein, as well as the classifiers per se, is that, due to the vanes of the impellers of the various classifiers being relatively long and extending longitudinally of the casings in spaced relationship and substantially parallel to the side. walls. of said casings, said vanes continually disturb and break up any tendency for unbalanced loading of one portion. of the classifier as opposed to another, whereby stratifying or agglomeration the fluidcurrents; While passing through the classifier is minimizedto a far greater degree. than has been possible in any classifiers heretofore produced.

While desirable. results may be obtained by impellers not provided with shielding means, the provision of shielding. means in the. impellers, as illustrated in the embodiments shown in Figs. 11 and 3, enhances the cleaning of the oversize particles and the power consumption is somewhat reduced which also results in less wear on the movable. part of the classifier. The inclusion of shielding means: in the impeller also defines a more precise and restricted annular passage for the stream through the classifier and results in an increase in speed of the stream through this more restricted annular passage as compared with the embodiments of classifiers in which no shielding means are included. Such increase in speed of the stream effects greater buoyancy of the particles in the stream without requiring additional impeller or fan power which would be required if no shielding meanswere included.

Further, the winnowing of the fluid stream while passing through the various embodiments of classifiers is accomplished in such a manner that a wavering of the stream toward and away from the axis of the impeller is caused, thereby insuring engagement of the stream by the vanes of the impeller and the centrifugal current effects produced thereby so as to effect positive removal of the coarser particles from said stream.

A number of embodiments of apparatus have been illustrated herein utilizing the same basic principles of the invention. However, each of the described embodiments includes certain details which produce particular advantages under certain conditions of use and related structure. Thus, while each embodiment is operable to perform the objects of the invention, the described embodiments are not equivalents and the embodiment illustrated in Figs. 1 and 2 is considered the preferred one.

While the invention has been shown and illustrated in its several preferred embodiments, and has included certain details, it should be understood that the invention is not to be limited to the precise details herein illustrated and described since the same may be carried out in other ways falling within the scope of the invention as claimed.

I claim:

1. A method of classifying coarse materials and fine materials comprising feeding a fluid stream containing a mixture of said particles to and through a classifying 11 area in a direction substantially axially of said stream, subjecting said stream to a selected rate of winnowing by varying the cross-sectional conditions of said stream to cause said stream to waver toward and from the axis thereof to prevent Stratification and to effect deflection of coarse material from said stream while being winnowed.

2. Apparatus for classifying coarse and fine material from a mixed fluid stream thereof and comprising an impeller having a shaft, a pair of members fixed transversely to and spaced longitudinally of said shaft, and a plurality of fluid impelling vanes extending between and peripherally spaced around said members, the upper ends of said vanes extending beyond one of said members; means supporting said shaft of said impeller for rotation about its axis; and a casing having side walls surrounding said impeller in spaced relationship to said vanes and substantially parallel thereto, said casing having an entrance at one end arranged to introduce a fluid stream of mixed particles into said casing adjacent one of said transverse members in a direction substantially perpendicularly thereto and said casing having an exit adjacent the opposite end thereof, said one of said transverse members being a baflie arranged to inhibit free movement of said stream in an axial direction.

3. Apparatus for classifying coarse and fine material from a mixed fluid stream thereof and comprising an impeller having a shaft, a pair of transverse members fixed to and spaced longitudinally of said shaft, a plurality of fluid impelling vanes extending between and peripherally spaced around and fixed to said members, and a substantially imperforate shield means extending between said members and also between said blades adjacent the inner edges thereof; means supporting said impeller for rotation about the axis of the shaft thereof; and a casing surrounding said impeller in spaced relationship to said vanes and generally parallel thereto, said casing having an entrance at one end arranged to introduce a fluid stream of mixed particles into said casing adjacent one of said members in a direction substantially perpendicularly thereto for movement through the space between said shield and said casing to an exit adjacent the opposite end of said casing.

4. The classifying apparatus of claim 3 further characterized by one end of said vanes extending beyond the member nearest the exit end of said casing.

5. Apparatus for classifying coarse and fine material from a mixed fluid stream thereof and comprising an impeller having a shaft, a pair of transverse plate-like members fixed to and spaced longitudinally of said shaft, a plurality of fluid impelling vanes extending between and peripherally spaced around said members, and imperforate shield means extending between said members but spaced inwardly from the edges thereof, said shield means also extending between said blades adjacent the inner edges thereof; means supporting said impeller for rotation about the axis of the shaft thereof; and a casing having side walls surrounding said impeller in spaced relationship to said vanes and generally parallel thereto, said casing having an entrance at one end arranged to introduce a fluid stream of mixed particles into said casing adjacent one of said plate-like members in a direction substantially perpendicularly thereto for movement through the space between said shield and said side walls of said casing to an exit adjacent the opposite end thereof, the projection of the peripheries of said plate-like members beyond said shield means serving to restrict said space and thereby increase the speed of said stream through said space.

6. A classifier for separating relatively coarse particles from a fluid stream containing the same intermixed with relatively finer particles and comprising in combination, a casing having an entrance adjacent one end arranged to receive said fluid stream of mixed particles and an exit adjacent the other end, said stream being movable longitudinally through said casing, an impeller extending longitudinally of and mounted for rotation within said casing about an axis extending longitudinally thereof, said impeller comprising vertically spaced substantially flat plates extending transversely to said axis and vanes extending between and fixed to the perimeter portions of said plates and the outer edges of said vanes being spaced from the walls of said casing to provide a substantial annular space defined by said casing walls, the lower plate serving as a baffle to deflect coarser particles laterally from said stream and cause removal thereof by gravity and the vanes of said impeller when rotated serving to impinge other relatively coarse particles from said stream against the walls of said casing and also causing fluid currents to move waveringly from the walls of said casing toward said impeller, thereby to cause said stream to engage said impeller means as said stream moves generally longitudinally of said casing, and means arranged to direct said separated coarser particles from said casing.

7. A classifier for separating relatively coarse particles from a fluid stream containing the same intermixed with relatively finer particles and comprising in combination, a casing having an entrance adjacent one end arranged to receive said fluid stream of mixed particles and an exit adjacent the other end, said stream being movable longitudinally through said casing, an impeller extending longitudinally of and mounted for rotation within said casing about an axis extending longitudinally thereof, said impeller comprising a series of blades extending substantially longitudinally of said casing in s aced relationship thereto and radially to the axis of said impeller, shield means disposed between said blades adjacent the inner edges thereof, said blades being spaced peripherally around said impeller, thereby to provide a substantially annular space between said casing walls and impeller, said impeller when rotated serving to impinge the coarser particles from said stream against the walls of said casing and also causing fluid currents to move from the walls of said casing toward said impeller, thereby to cause said stream to engage said impeller as said stream moves generally longitudinally of said casing, and particle collecting means arranged to receive said separated coarser particles from said casing.

8. The classifier of claim 7 further characterized by said impeller and easing being arranged substantially vertically in use and said impeller also comprising top and bottom walls spaced vertically apart, said walls serving to deflect certain larger particles of material from said stream and cause the same to engage the walls of said casing and move to said particle collecting means.

9. The classifier of claim 8 further characterized by the upper ends of said blades extending above said top wall of said impeller.

10. A classifier for separating relatively coarse particles from a fluid stream containing the same intermixed with relatively finer particles and comprising in combination, a substantially cylindrical casing supported with its axis substantially horizontal and having an entrance adjacent one end arranged to receive said fluid stream of mixed particles, said stream being movable longitudinally through said casing, impeller means extending longitudinally of and mounted for rotation within said casing upon a horizontal axis extending longitudinally thereof, said impeller comprising a shaft having a pair of members fixed transversely thereto and spaced longitudinally thereon, at least one of said members being flat and disposed adjacent the entrance of said casing to serve as a battle against which incoming material impinges and is deflected to cause removal thereof by gravity, said impeller also having blades extending longitudinally of said casing between said members and fixed thereto and the outer edges of said blades being spaced from the walls of said casing to provide a substantially annular space defined by said casing walls, said impeller when rotated serving to impinge the coarser particles from said stream against the walls of said casing and also causing fluid currents to move from the walls of said casing toward said deflecting means, thereby to cause said stream to engage said impeller means as said stream moves generally longitudinally of said casing, and a particle discharge sump connected to and depending from the bottom wall area of said casing and arranged to receive the coarser particles separated from said stream as aforesaid.

11. A classifier for separating relatively coarse particles from a fluid stream containing the same intermixed With relatively finer particles and comprising in combination a substantially conical casing operatively supported I with the axis thereof extending substantially horizontally and having an entrance in the small end of said casing arranged to receive said fluid stream of mixed particles, said stream being movable longitudinally through said casing, impeller means extending longitudinally of and mounted for rotation Within said casing upon a horizontal axis extending longitudinally thereof, said impeller comprising a shaft having a pair of members fixed transversely thereto and spaced longitudinally thereon, at least one of said members being flat and disposed adjacent the entrance of said casing to serve as a baflie against which incoming material impinges and is deflected to cause removal thereof by gravity, said impeller also having blades extending longitudinally of said casing between said members and fixed thereto and the outer edges of said blades being spaced from the walls of said casing to provide a space which is annular in cross-section and is defined by said casing walls, said impeller when rotated serving to impinge the coarser particles from said stream against the walls of said casing and also causing fluid currents to move from the walls of said casing toward said deflecting means, thereby to cause said stream to engage said impeller means as said stream moves generally longitudinally of said casing, and a particle discharge sump connected to the bottom wall area of said casing adjacent the large end thereof and arranged to receive the coarser particles separated from said stream as aforesaid.

12. A classifier for separating relatively coarse particles from a fluid stream containing the same intermixed with relatively flue particles and comprising in combination, a casing substantially circular in cross-section and mounted with its axis substantially vertical, said casing comprising side walls and having an entrance at the lower end thereof arranged to receive a fluid stream of mixed particles and an exit at the upper end thereof, said stream being movable generally vertically through said casing, impeller means extending longitudinally of and mounted for rotation within said casing about an axis extending substantially vertically and comprising peripherally spaced vanes extending longitudinally of said casing and deflector means connected to said vanes to support the same for rotation in spaced relationship to said walls of said casing to provide a substantial annular space between said impeller means and said casing walls, said impeller means when rotated serving to impinge the coarser particles from said stream against the walls of said casing and said deflector means being on the lower portion of said impeller and operable to deflect certain coarse particles from said stream and against the walls of said easing, baffle means fixed to and extending substantially horizontally across said impeller means adjacent the upper end thereof and operable to receive coarser particles of material dropped thereon, the rotation of said baifle means causing discharge of said coarser particles from said plate against the sides of said casing, and means arranged to collect said coarser particles thus discharged.

13. The classifier of claim 12 further characterized by the upper ends of said blades extending above said baflle means and operable to induce eddy currents directed toward the upper surface of said baffle and effective to cause particles of coarser material to be deposited thereon, said particles then being subject to centrifugal force to impinge the same against the walls of said casing.

14. The classifier of claim 12 further including scraper mechanism mounted stationarily relative to said casing and adjacent the upper surface of said baffie means, whereby rotation of said baifle means relative to said scraper serves to scrape accumulated material from said bafiie means and into said fluid stream.

15. A classifier for separating relatively coarse particles from a fluid stream containing the same intermixed with relatively fine particles and comprising in combination, a casing substantially circular in cross-section and mounted with its axis substantially vertical, said casing having an entrance at the lower end thereof arranged to receive a fluid stream of mixed particles and an exit at the upper end thereof, said stream being movable generally vertically through said casing, impeller means extending longitudinally of and mounted for rotation within said casing about an axis extending substantially vertically and comprising peripherally spaced blades extending longitudinally of said casing and vertically spaced means extending transversely to said vertical axis, said blades extending between and connected to said transverse means for support in spaced relationship to the walls of said casing to provide a substantially annular space defined by said casing walls, the lowermost of said transverse means also comprising deflector means positioned adjacent the entrance of said casing and extending transversely to the axis of said casing adjacent said entrance, and shield means extending between said blades and said vertically spaced means, said deflector means when rotated serving to deflect the coarser particles from said stream against the walls of said casing and the blades of said impeller when rotated serving to impinge other coarser particles against said casing walls and also induce fluid currents to move from the walls of said casing toward said impeller, the uppermost of said transverse means comprising baffle means fixed to and extending substantially horizontally across said impeller means adjacent the upper end thereof and operable to receive coarser particles of material dropped thereon, the rotation of said lbaffle means inducing centrifugal force causing discharge of said coarser particles from said plate against the sides of said casing.

References Cited in the file of this patent UNITED STATES PATENTS 1,664,092 Squires Mar. 27, 1928 1,810,922 Mil-ls June 23, 1931 1,898,807 Barnes Feb. 21, 1933 2,153,270 Osgood Apr. 4, 1939 FOREIGN PATENTS 535,238 Germany Oct. 8, 1931 

3. APPARATUS FOR CLASSIFYING COARSE AND FINE MATERIAL FROM A MIXED FLUID STREAM THEREOF AND COMPRISING AN IMPELLER HAVING A SHAFT, A PAIR OF TRANSVERSE MEMBERS FIXED TO AND SPACED LONGITUDINALLY OF SAID SHAFT, A PLURALITY OF FLUID IMPELLING VANES EXTENDING BETWEEN AND PERIPHERALLY SPACED AROUND AND FIXED TO SAID MEMBERS, AND A SUBSTANTIALLY IMPERFORATE SHIELD MEANS EXTENDING BETWEEN SAID MEMBERS AND ALSO BETWEEN SAID BLADES ADJACENT THE INNER EDGES THEREOF; MEANS SUPPORTING SAID IMPELLER FOR ROTATION ABOUT THE AXIS OF THE SHAFT THEREOF; AND A CASING 